The calculated distance (air line) between Taesal-li and Seongnam-si is approximately 50 miles respectively 80 kilometers.
By car or train, the actual journey to Seongnam-si is certainly longer, as only the direct route (as the crow flies) between Taesal-li and Seongnam-si has been calculated here.
Air line (approximately)
80 kilometers
43 nautical miles